This experiment tests if hardwoods generate more heat in the fireplace than softer woods, because of increased density. The tester uses oak, pine, cedar and maple, three pieces of each, cut to the same size. Allow each type of wood to burn for a minute, then set a beaker of room-temperature water over the burning wood for five minutes. Measure the changes in temperature each minute. After five minutes, record the final water temperature. Students also could measure the time it takes for wood to burn down to ashes or use a thermometer to measure the flame temperature.
Use mirrors to maximize solar cell efficiency in terms of photovoltaic output. Because even the most efficient solar cells only convert as much as 16 percent of solar energy into electricity, increasing the intensity of that energy is crucial for meaningful electrical production. Connect a solar cell to a voltmeter and ammeter and tested efficiency under three conditions: without any reflector, with a flat mirror and with a parabolic mirror. The parabolic mirror focuses light the best and should produce the highest output. Other factors that would make interesting experiments include the effects of temperature change on solar cell operation, by operating the cells indoors with the same level of light at different temperatures.
Younger children are introduced to the relationship between density and buoyancy. You'll need cans of different brands of soda, some with sugar or high-fructose corn syrup, and others that are diet, with artificial sweetener. Put the stopper in a kitchen sink and fill it about three-quarters full with water, and then put in the soda cans. Some of the cans will float and others will sink to the bottom, because some sodas are denser than water and others are not as dense, depending on their contents. Note with your children which cans float and which ones sink, and identify what ingredients the floating cans and the sinking cans have in common.
This project will help you and your child put together a balloon hovercraft. Using a blank CD-ROM, a piece of cardboard, some PVC pipe and a balloon, you can make a small craft that will hover above flat surfaces. Glue cardboard to both sides of the center of the CD-ROM, covering the hole. Poke a small hole through the center of the cardboard and glue the PVC pipe in place above the hole. Attach the air-filled balloon to the top of the pipe, give the craft a slight lift and push, and it will hover. This demonstrates the power of air pressure, which is also at work in the hovercraft used for transportation.